function lazyLoad() {
    var visualViewport = window.innerHeight || document.documentElement.clientHeight
    var scrollTop = document.body.scrollTop || document.documentElement.scrollTop
    var maxShowHeight = visualViewport + scrollTop
    var imgs = document.querySelectorAll('img')
    imgs.forEach(function (item) {
        if (item.offsetTop < maxShowHeight) {
            item.src = item.getAttribute('src-real')
        }
    })
}